System, Method, and Conversion Kit for Controlling Smoke during Air Frying in a Range or Oven

ABSTRACT

Embodiments of this disclosure reduce an oven&#39;s emission of volatile organic compounds when air frying. The catalyst does not require a self-contained heating assembly but instead is adapted for connection to at least one of a suction side and a discharge side of the circulation fan. The catalyst may be in the form of a screen or a foil bundle and have a mass loading of 10 g to 75 g per cubic foot of catalyst volume. The screen is sized for connection to the circulation fan and includes a corrugated pattern and coated with the catalyst on at least half of the screen. The foil bundle has a cell density in a range of 20 cells to 50 cells per square inch and is sized for location in a corner of the heating elements. The foil bundle can include a slew or herringbone cell pattern.

CROSS-REFERENCE TO CO-PENDING APPLICATIONS

This application claims priority to U.S. 63/302,850 filed Jan. 25, 2022 and U.S. 63/381,053 filed Oct. 26, 2022.

BACKGROUND

This disclosure is in the field of appliances used for cooking and, in particular, catalytic devices used in connection with a range or oven to control odors and smoke.

Residential appliance manufacturers have recently introduced oven models that incorporate cooking techniques that utilize rapid recirculation of hot air in the oven cavity to “fry” foods in a manner that is perceived to be healthier than conventional deep fat frying.

These cooking techniques can generate large quantities of smoke that are emitted from the oven vent or can leak through various pathways in the oven cavity. These smoke emissions are viewed as a negative experience by the users and as a result the appliance manufacturers have received many complaints and disgruntled users have posted videos and comments on social media sites.

U.S. Pat. No. 8,418,684 B2 to Robinson, Jr. (“the '684 patent”) reviews prior art for a catalytic converter unit for use in combination with an oven for treating odiferous emissions emanating from an oven cavity of a residential range or oven during cooking. The '684 patent discloses a system and method that include a housing that contains an electric heating element and a catalyst unit. The housing may connect to other components of the range or oven to complete the venting of the exhaust from the range or oven. The electric heating element is arranged so that infrared radiation from the hot surface of the element is visible by the inlet face of the catalyst. The power output of the heater is sized so that the catalyst reaches a minimum operating temperature to initiate the catalytic reaction in advance of the temperature increase in the air coming from the cavity. The system and method destroy the odors that come from the cooking process so as to improve the cooking experience. The subject matter of the '684 patent is incorporated by reference herein.

Different cooking cycles within the oven cavity create air flows and air flow temperatures and, therefore different emissions and different rates of emissions. The catalytic conversion unit of the '684 patent is intended for a cooking cycle like baking, where there is a natural draft air flow. For example, in a cooking cycle like baking a fan typically draws air from the middle of the cooking chamber and circulates it around the cooking chamber, the heated air flowing around the food item being cooked. However, in a cooking cycle like air frying, an active air flow is used, in which the fan reverses direction, blowing air into the middle of the cooking chamber with the heated air flowing directly to the food item. Because the air is nearer to the heating elements when blown, the air contacting the food item is at a higher temperature during air frying than it would be during baking. Air frying causes aerosolized grease droplets in certain foods that can cause smoking.

SUMMARY

Embodiments of this disclosure are adapted for use in an oven including an air frying mode, a cooking chamber containing a circulation fan on a wall of the cooking chamber, and a plurality of heating elements adjacent to and surrounding the fan to form four corners located about the fan. A catalyst is located on the inlet or suction side of the circulation fan. The catalyst can eliminate the smoke to a level that is nearly non-existent or at least would not be observable or objectionable to the user. The catalyst is composed of a substrate, such as a woven wire cloth, expanded metal, or permeable paper-like material that is impregnated with a catalytically active coating comprised of a high surface area aluminum oxide based washcoat and an active component or components. The shape of the substrate can be round, square, rectangular or any other geometric shape that is selected to provide sufficient coverage to achieve the necessary performance.

In one embodiment, a screen including a corrugated pattern is coated with the catalyst on at least half of the screen. The catalyst includes a precious metal having a mass loading in a range of 20 g to 50 g per cubic foot of catalyst volume. The screen is sized for installation on the inlet or suction side of the circulation fan and includes means for connection to the inlet or suction side of the circulation fan. Without the screen installed the oven emits a first amount of volatile organic compounds when cooking a predetermined food in air fry mode under predetermined conditions. With the screen installed the oven emits a second amount of volatile organic compounds at least 95% lower than the first amount of volatile organic compounds when cooking the predetermined food in the air fry mode under the predetermined conditions.

In another embodiment of this disclosure, one to four metal foil catalysts are used. Each metal foil catalyst is located between a corresponding one of the four corners and the fan. A baffle cover plate then covers the fan, the plurality of heating elements, and the one to four metal foil catalysts.

In methods of this disclosure for treating emissions of an oven when air frying, the emissions pass through the catalyst from the cooking chamber and into an exhaust vent of the oven.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of an example embodiment of a catalytic system of this disclosure.

FIG. 2 is a top perspective schematic type depiction of a generic residential range or oven showing the catalytic conversion unit in assembled relation with the oven or range.

FIG. 3 is a cross-sectional side view of the range or oven of FIG. 2 outfitted with the catalytic conversion unit of the present invention.

FIG. 4 is an enlarged, upper right section of the range or oven of FIG. 3 , showing the structures defining an emission pathway.

FIG. 5 is a front elevation, exploded assembly view of the catalytic system of FIG. 1 .

FIG. 6 is a partial, front elevation view of the left hand side of the catalytic system of FIG. 1 .

FIG. 7 is a bottom view of the left hand side of the catalytic system of FIG. 1 .

FIG. 8 is a cross-section, front elevation view of the left hand side of the catalytic system of FIG. 1 .

FIG. 9 is a top perspective, exploded assembly view of the catalytic system of FIG. 1 with the upper catalytic screens removed.

FIG. 10 is a graph comparing emissions during a test of the catalytic system of this disclosure (“CCC Catalyst”) during a self-cleaning cycle of the residential range or oven with those of a prior art catalytic system (“OEM Catalyst”).

FIG. 11 a graph comparing emissions during a test CCC Catalyst when cooking bacon in the residential range or oven with those of the OEM Catalyst.

FIG. 12 a graph comparing emissions during a test CCC Catalyst when cooking a turkey in the residential range or oven with those of the OEM Catalyst.

FIG. 13 a graph comparing emissions during a test CCC Catalyst when cooking chicken wings in the residential range or oven with those of the OEM Catalyst.

FIG. 14 is a graph comparing total emissions of the CCC Catalyst with those of the OEM Catalyst during a first and second cooking cycle of the chicken wings.

FIG. 15A is an embodiment of a minimum diameter exhaust port used in an embodiment of a residential range or oven configured with an air frying mode. The exhaust port may be the same size diameter as the inlet port or may be a different size diameter. In embodiments, the exhaust port may be a 7 mm diameter exhaust port.

FIG. 15B is an embodiment of a maximum diameter exhaust port used in an embodiment of a residential range or oven configured with an air frying mode. Again, the exhaust port may be the same size diameter as the inlet port or may be a different size diameter. In embodiments, the exhaust port may be a 36-¾ mm diameter exhaust port.

FIG. 16A illustrates the location of the inlet boundary condition for the exhaust through the ports of FIGS. 15A & 15B.

FIG. 16B illustrates the location of the outlet boundary condition for the exhaust through the ports of FIGS. 15A & 15B.

FIG. 17A is first layer mesh screen velocity profile for the minimum diameter exhaust port of FIG. 15A.

FIG. 17B is a second layer mesh screen velocity profile for the minimum diameter exhaust port of FIG. 15A.

FIG. 17C is a side elevation view of the velocity profile through the first and second layers for the minimum diameter exhaust port of FIG. 15A.

FIG. 18A is first layer mesh screen velocity profile for the maximum diameter exhaust port of FIG. 15B.

FIG. 18B is a second layer mesh screen velocity profile for the maximum diameter exhaust port of FIG. 15B.

FIG. 18C is a side elevation view of the velocity profile through the first and second layers for the maximum diameter exhaust port of FIG. 15B.

FIG. 19A is an embodiment of a corrugated screen catalyst of this disclosure encased in a rim structure to capture the raw edges of the substrate material and arranged for installation to a circulation fan cover of an oven. The catalyst can eliminate the smoke to a level that is nearly non-existent or at least would not be objectionable to the user.

FIG. 19B is a front elevation view of the catalyst in the installed state.

FIG. 19C is an isometric view of the catalyst of FIG. 19A in an installed state.

FIG. 20 is an embodiment of a corrugated screen catalyst of this disclosure including a rim structure with clips.

FIG. 21 is another embodiment of a corrugated screen catalyst of this disclosure including a rim structure with tabs.

FIG. 22 is a chart comparing hydrocarbon emissions using embodiments of a corrugated screen catalyst of this disclosure over time (from 1 second to 9,107 seconds (about 152 minutes)).

FIG. 23 is a chart comparing hydrocarbon emissions of an oven with air fryer as built and as modified using a corrugated screen catalyst of this disclosure.

FIG. 24 is a chart comparing hydrocarbon percent conversion using a corrugated screen catalyst of this disclosure.

FIG. 25 is a chart comparing particulate matter.

FIG. 26 is a chart comparing particulate matter % conversion using a corrugated screen catalyst of this disclosure.

FIG. 27 is a photograph of a baffle cover plate found at the back of an oven. The plate covers the heating elements, fan, and catalyst of this disclosure. This plate is but one of many different types of fan covers or baffle plates used in the art and is provided here for illustrative and non-limiting purposes.

FIG. 28 is photograph of a catalyst of this disclosure located in a lower corner of the heating elements, between the heating elements and the fan.

Elements and Numbering used in the Drawings

-   -   10 Heated screen catalyst assembly     -   11 Cooking chamber     -   12 Residential range or oven with air frying mode     -   13 Range or oven door     -   14 Housing     -   15 Inlet to heated screen catalyst assembly     -   16 Thermal radiation source     -   17 Circuitry for connection to power source     -   18 Screen catalyst     -   19 Outlet from heated screen catalyst assembly     -   20 Untreated emissions     -   21 Emission path     -   22 Treated emissions     -   23 Outlet     -   25 Looped members of thermal radiation source     -   30 Vent tube     -   31 Rim structure     -   40 Foil catalyst     -   41 Frame     -   43 Heating element     -   45 Fan     -   47 Baffle cover plate     -   49 Heating element corner     -   G Grease path

Referring first to FIGS. 1 to 9 , embodiments of a heated screen catalyst assembly 10 of this disclosure is configured for use with a residential range or oven 12 that includes an air frying mode. The assembly 10 may be housed within the oven 12, with its inlet 15 exposed to the cooking chamber 11 of the oven 12. A housing 14 contains the assembly 10 and connects either directly or through the use of ancillary components to the cooking chamber 11 and to an outlet 23 of the oven 12. This provides a path for emissions during cooking or air frying from the chamber 11 to the outlet 23. Contained in the housing are an electric heating element or thermal radiation source 16 and a catalyst screen 18.

In embodiments, the catalyst screen 18 is in the form of a wire mesh cloth located on opposite sides of the radiation source 16. The one catalyst screen 18 is located closer to the inlet 15. The radiation source 16 heats the air entering the inlet 15 as well as the screen 18. This first screen 18 may be slightly hotter, at least initially, than the second screen 18, but the radiation source 16 tends to equilibrate the two screens 18. The screens 18 may also be hotter than the oven cavity depending on what is programmed for the cook cycle, which may be an air-frying cook cycle. By way of a non-limiting example, the catalyst screen 18 may be in a range of 600° F. to 650° F., the oven cavity being in a range of 400° F. to 425° F.

The first screen 18 may be more surface heat reactive than the second screen 18, which receives air that has passed through the first screen 18 as well as the radiation source 16. The air may be at its maximum temperature at the second screen 18. See e.g. FIGS. 16A ff. Unlike the '684 patent, the degree of control needed in the heated screen catalyst assembly 10 is not as stringent a requirement. The catalyst screen 18 in close proximity to the radiation source 16 superheats the screen 18 at a much higher temperature than air temperature flowing throughout.

Emissions during cooking or air frying follow an emissions path 21 in which the emissions enter the inlet 15 of assembly 10 as untreated emissions 20, pass through the catalyst screen 10, and exit the outlet 19 of the assembly 10 as treated emissions 22 which are then exhausted or vented through an outlet 23 of the oven 11.

In embodiments, catalyst element 18 is a screen catalyst. The screen catalyst may include a wire mesh cloth having a high surface area aluminum oxide coating that has been impregnated with catalytically active elements. Other substrate formats such as expanded metal or metal foil or ceramics could be used. The catalytically active elements may be a platinum only element. In other embodiments, it may be a platinum and palladium blend (although platinum only performed better during air frying). The coating may be a mixture of two aluminum oxide phases, such as the gamma and boehmite phases. Other elemental oxides may be present in lesser amounts to act as thermal stabilizers or to enhance the effectiveness of the catalytically active elements. The oxides are prepared and applied in a manner well known to those skilled in the art.

The mesh size of the screen catalyst should be selected to provide sufficient heat reactive surface area without causing excessive pressure drop. In embodiments, the screen catalyst may in a range of a size 10 mesh wire cloth to a size 50 mesh wire cloth, there being discrete values and subranges within this broader range. In some embodiments, a size 30 mesh wire cloth was used. The mesh size should also be selected so that the oven can pass fire and explosion tests like those performed by Underwriters Laboratories (restriction to flow in the vent 23 can blow door 13 open during a fire or other extreme temperature event). In tests, the 30 mesh wire cloth provided good balance between reactive surface pressure and pressure drop.

To maintain a consistent operating or catalytic temperature, a catalytic conversion unit of this disclosure includes a thermal radiation source 16. The heated screen catalyst assembly 10 depends upon the source 16 for a consistent operative temperature of its catalytic elements 18, making the heated screen catalyst assembly 10 unaffected by temperature variations caused by a user opening the door 13 of the cooking chamber 11 during air frying or cooking. In embodiments, thermal radiation source 16 may include one or more looped members 25 being arranged in a same plane as one another. Adjacent to, spaced apart from, and overlapping the looped members 25 is at least two catalyst mesh or screen catalysts 18 arranged parallel to the looped members 25, each located on opposite sides of the looped members 25. In some embodiments, at least two layers of screen catalysts 18A, 18B are located on one side of the looped members 25 and another at least two layers of screen catalysts 18C, 18D are located on the other side of the looped members 25.

Referring now to FIG. 10 , tests of a heated catalyst assembly of this disclosure were performed using ½ cup of an OEM “monster mash” recipe in an Electrolux oven with air frying mode during the oven's self-clean setting over a period of three hours. The catalyst temperature within the heated screen catalyst assembly was 650° F. The prior art (“OEM Catalyst” relied on heat from the oven chamber to initiate the reaction. Due to heat transfer effects, it lagged behind the pyrolysis of the baked on food soil. Since the heater overcomes the heat transfer issues, the screen catalyst 18 activates faster, resulting in far less emissions. The screen catalyst of this disclosure, labeled as the “CCC Catalyst” in the figure, reduced the overall emissions by 54% compared to OEM Catalyst. The OEM Catalyst peaked at 204 PPMv of emissions. The CCC Catalyst peaked at 66 PPMv of emissions.

In other tests of embodiments of this disclosure, bacon was air fried in the Electrolux oven using the following parameters for each test:

-   -   Amount of Bacon: 1 lb per pan     -   Number of Cycles: 3     -   Oven Temperature: 350° F.     -   Cook Time: 20 minutes     -   Dwell Time: 5 minutes     -   Oven Setting: Air Fry Mode     -   CCC Catalyst Temp: 650° F.         The OEM catalyst peaked at just under 6 PPMv for emissions at         the largest peak. See FIG. 11 . Because air frying bacon in the         oven 12 does not lead to complaints of smoking, this implies         that achieving fewer than 6 PPMv is “acceptable” for emissions.         The CCC Catalyst had 49.4% reduction in emissions compared to         the OEM Catalyst with an average of 0.34 PPMv. It was observed         that a fair amount of steam came out of the vent 23 during         testing of both catalysts.

In other tests of embodiments of this disclosure, a whole turkey test was conducted with the CCC Catalyst installed in the oven 12. A 23 lb whole turkey was used. The cooking parameters were:

-   -   Oven Temperature: 350° F.     -   Cook Time: 4 hours     -   Oven Setting: Air Fry Mode     -   Catalyst Temperature: 650° F.         There were practically no emissions and very little steam. See         FIG. 12 .

In other tests of embodiments of this disclosure, chicken wings were cooked on air fry mode. The cooking parameters used in the tests were as follows:

-   -   Amount of Chicken: 3 lbs per pan     -   Number of Cycles: 3     -   Oven Temperature: 450° F.     -   Cook Time: 35 minutes     -   Oven Setting: Air Fry Mode     -   CCC Catalyst Temperature: 650° F.     -   Dwell Time: 10 minutes (Sequential runs only)         The CCC Catalyst reduced emissions by about 84% compared to the         OEM catalyst. See FIG. 13 . Cooking sequential trays of wings         proved repeatability and showed that the catalyst of this         disclosure has the capability to keep up with an high load usage         condition. Even under these strenuous conditions, the CCC         catalyst had a peak emissions point of 4.3 ppmv vs 33.4 ppm for         the OEM catalyst.

Referring now to FIG. 14 , as the tests consistently show, a heated screen catalyst assembly 10 of this disclosure is capable of dramatically reducing both the odorous and smoke emissions from the air frying of chicken wings; that practically zero emissions come from bacon and whole turkey cooked on the air fryer setting; and the heated catalyst screen assembly 10 significantly improves the self cleaning performance of the oven when the heater is energized during the initial portion of the self-cleaning cycle.

Referring now to FIGS. 19A to 26 , in other embodiments the catalyst is not contained in a self-contained heated catalyst assembly 10 but is instead a screen catalyst 18 or metal foil catalyst 40 connected to the fan 45 of the cooking chamber 11. The catalyst can eliminate the smoke to a level that is nearly non-existent or at least would not be observable or objectionable to the user. In embodiments, the catalyst is composed of a substrate, such as a woven wire cloth, expanded metal, or permeable paper-like material that is impregnated with a catalytically active coating comprised of a high surface area aluminum oxide based washcoat and an active component or components. The shape of the substrate can be round, square, rectangular or any other geometric shape that is selected to provide sufficient coverage to achieve the necessary performance.

Mass loading of the precious metal content may be in a range of 10 g to 75 g per cubic foot, and more specifically in the range of 20 g to 50 g per cubic foot, of catalyst volume, there being subranges and discrete values within this broader range. A portion of the substrate may include the catalyst and another portion may not (e.g. 25% to 75% of the screen is coated). For example, a lower or upper half (or right or left half) of the substrate may be coated with catalyst and the corresponding half uncoated. In embodiments, 50% to 100% of the substrate is coated, there being subranges and discrete values within this broader range.

Before being coated the substrate may have a pattern impressed upon it to increase the active surface area contained within the physical dimensions of the selected shape. The washcoat layer may be co-impregnated with other chemical elements that promote the overall reaction, or protect the coating from temperature induced degradation, or protect the active components from deactivation caused by the accumulation of materials that are poisonous to the active component's functionality. The washcoated substrate is subsequently coated with an active component that can be solely comprised of various combinations of platinum group metals, such as platinum and/or palladium, or mixtures of platinum group metals and other base metals from Groups 3 through 12 of the Periodic Table.

The ability to coat the substrate with a complete coating that is a combination of the washcoat materials, any promoter of types known in the art, and the active components in a single operation rather than a sequence of operations is also within the scope of this disclosure.

The coated substrate may be encased in a rim structure 31 to capture the raw edges of the substrate material. The rim structure 31 can be made from various grades of stainless steel, 304SS being preferred, or grades of aluminum alloy capable of withstanding oven temperatures up to 850° F., or aluminized steel. The rim structure 31 also provides locations for the attachment of mechanical fastening methods to hold the catalyst screen 18 in place inside the oven. Among the type of fastening systems are wire ties, springs, clips, tabs, or magnets.

In some embodiments, the catalyst screen 18 is installed into the oven on the inlet or suction side of the circulation fan which is typically located on the back wall of the oven cavity. Installation in this location ensures that all the air being circulated by the fan encounters the active surface of the catalyst. Furthermore, this location does not impose a static pressure on the discharge from the circulation fan that can impede the cooking performance of the oven which is dependent upon the volume and velocity of the circulating air to “fry” food within the cooking chamber of the oven. However, because some ovens do not reverse the flow of the fan, in other embodiments the catalyst screen 18 may be installed on the discharge side of the circulation fan. Because of the structure of the catalyst substrate, when installed on the discharge side there is minimal effect on static pressure and air volume or air velocity needed for proper cooking.

One embodiment of this disclosure utilized a 30-mesh woven wire cloth made from 304Ss that was corrugated with a herringbone or zig-zag pattern to increase its surface area and rigidity. The substrate was subsequently coated with an aluminum oxide washcoat that was impregnated with rare earth oxides before being impregnated with a platinum-only active layer. Mass loadings of 25 g, 26 g, 35 g, and 46 g per cubic foot of catalyst volume of the precious metal content were prepared. A commercially available residential oven that features an “AirFry” mode was obtained for the trials.

Prior to the catalyst being installed, the oven was run through the AirFry cycle several times with no food in it to break in the oven. This eliminated any volatile compounds that remained from the manufacturing process or off gas from the insulation that wraps the oven cavity. Then cook cycles without the catalyst being installed were done with the following parameters to establish a baseline of uncontrolled emissions:

-   -   Amount of Chicken: 3 lbs per tray     -   Number of Cook Cycles/Trial: 3     -   Oven Temperature: 450° F.     -   Cook Time: 35 minutes     -   Oven Setting: Air Fry Mode     -   Dwell Time: 10 minutes (Sequential runs only)     -   AirFry tray in rack position 3 and drip tray in rack position 1     -   20 minute dwell after last tray to collect any residual         emissions

“Generous” coating of PAM® cooking spray applied to each tray prior to cooking in accordance with the oven manufacturer's instructions.

The cooking process was repeated with the catalyst being wired in place on the intake side of the circulation fan cover. Two types of data were collected during the baseline and catalyst equipped cooking trials. One was a filter catch to measure solid smoke particles and condensable organic compounds which comprise the visible smoke emissions from the oven. The other was a total hydrocarbon concentration using a Flame Ionization Detector (“FID”) which measures the concentration of volatile organic compounds that comprise the odor of the emissions.

-   -   The catalyst achieved the following reductions:     -   Visible Smoke Constituents 97.8%     -   Volatile Organic Compounds 98.0%

The smoke emissions from the oven for the catalyst-equipped trial were essentially invisible to the eye in comparison to the noticeable smoke plume seen during the baseline trial. A thermal image of embodiments of the full screen catalyst during the cooking cycle had shown a temperature rise in one half of the catalyst. Therefore, the half-coated screen was an experiment to see if that phenomenon translated to acceptable conversion performance. The half-coated screen did perform better than a complete screen with an overall lower precious metal content but did perform as well as the fully-coated screen with higher precious metal content. Therefore, the half-screen can be used if lower cost is desired and if lessened performance is acceptable to a user or oven manufacture. In comparison it did perform better than a complete screen with an overall lower precious metal content. This suggests that the area density of the precious metals is key to the performance over the total mass loading.

A screen catalyst may be useful in ovens where the geometry of the internal baffle cover plate for the back of the cavity does not allow for a foil catalyst. (The baffle cover plate, along with a fat filter, protect the oven fan from grease and food splatter.) In other ovens, the size of baffle cover plate may permit use of a foil catalyst. Foil catalysts have higher levels of surface area on which the catalytic reaction can take place. Catalyst performance is proportional to the amount of geometric surface area of the catalyst substrate.

Unlike embodiments of this disclosure that include a self contained unit with heater and catalyst or make use of the screen catalyst, embodiments that make use of a metal foil catalyst 40 are located behind the baffle cover plate 47 over the circulation fan 45/heater 43 section in the back of the oven. The foil catalyst 40 is sized to fit within space constraints of the area between the heating element corners 49 and fan 45 in the back of the oven (see e.g. FIG. 27 ). The frame 41 in which the catalyst 40 is contained may be any material suitable. The frame can change based on the method by which it is secured to the oven (e.g., screws or rivets through tabs, tabs that fit into slots in the oven, clips that attach it to the heater element, etc.). The source plane of the radiation source, that is, heating elements 42, run parallel to the emission receiving surface of the catalyst element 40.

By way of a non-limiting example, a foil catalyst 40 of this disclosure may be 5.80″ length (fold to fold), 0.75″ height, and 1.00″ width (foil thickness). These dimensions may be adjusted if, for example, an oven manufacturer specifies a minimal clearance zone around the fan 45. In embodiments, the cell density of the foil substrate may be in a range of 20 to 50 cells per square inch and provide a desired flow path, there being subranges and discrete values within this broader range. The cell patterns may be skew or herringbone. For example, in one embodiment the substrate included 45 cells per square inch using a skew flow path design. Mass loadings in a range of 10 g to 75 g, more specifically 20 g to 50 g per cubic foot of catalyst volume may be used for the precious metal loading, there being subranges and discrete values within this broader range. The catalytically active elements may be a platinum only element. In other embodiments, it may be a platinum and palladium blend.

Because catalysts perform better at higher temperatures, and because catalytic effectiveness was found to be dependent on the amount of oven-chamber air that is routed through the catalyst, in embodiments foil catalyst 40 arranged as foil bundles were placed in the four corners 49 of the heating element 43, see FIG. 27 , to process a large portion of the air being circulated by the fan as it exits the baffle cover plate 47. For purposes of this disclosure, a foil bundle is a length of coated foil that is folded back and forth to create a stack of length and height for a given foil flow thickness. It can be tied with stainless wire or encapsulated with a stainless steel frame prior to installation into the oven.

After a successful smoke test with the four foil bundles, the bundles were removed to test effectiveness of smoke reduction for three, two, and one foil bundle arrangements. During the removal of foil bundles, grease paths G on the baffle cover plate 47 indicated a region of high flow in the lower left-hand corner 49. See FIG. 27 . Therefore, with one foil bundle placed in the bottom left-hand corner, see FIG. 28 , a successful smoke test was achieved. Due to the inherent design of air fry along with the catalyst placement, the air is recycled through the catalyst multiple times rather than a single-pass design where the catalyst is placed in the oven exhaust duct. The number of foil catalyst bundles, and the size of the bundles, used in an application to achieve a desired level of smoke and order control can be determined based on the oven manufacturer's marketing goal, target foods to be cooked, and the parameters of the oven's cooking cycle (e.g., temperature, air circulation rate, chamber volume).

In embodiments, cell density and precious metal loadings were modified and adjusted and tested per the following table, where the precious metal loading standard is about 35 g per cubic foot of catalyst volume:

Precious Metal Volume Hydrocarbon Loading Cell Density (% of Control PM Control Catalyst (% of Standard) (cpsi) Standard) (% DRE) (% DRE) Formulation B 100% 45  100% 79.8% 89.66% Formulation D  71% 45  100% 44.3% 79.31% Formulation E 143% 100 66.4% 49.3%  6.90% Formulation F 143% 150 66.4% 61.9%  0.31%

A reduction in precious metal loading resulted in a dimensioned hydrocarbon control, which was a good proxy for overall catalyst performance (Formulation D), and there was a noticeable increase in the visual levels of smoke from the oven as well. The modification in volume and cell density (Formulations E and F above) helped achieve a greater clearance between the fan and the catalyst. However, increasing the cell density resulted in a significant loss of performance and visual smoke levels similar to a “No Catalyst” condition. This was likely a result of increased pressure drop and providing a path of “most resistance” (through the catalyst), resulting in limited air flow being processed by the catalyst.

The following catalyst orientations with the catalyst from Formulation B:

-   -   ▪ 0° degree orientation         -   No visible smoke at 425° F. for 25 minutes         -   No visible smoke at 425° F. for 35 minutes     -   15° degree orientation         -   No visible smoke at 425° F. for 25 minutes         -   No visible smoke at 425° F. for 35 minutes     -   45° degree orientation         -   Small amounts visible smoke at 425° F. for 25 minutes         -   Small amounts of visible smoke at 425° F. for 35 minutes             In tests conducted it was learned that temperature is a             driving force of smoke rather than the time spent at each             temperature. For example, 425° F. for 35 minutes produced no             smoke whereas 450° F. for 25 minutes produced smoke.

Embodiments of this disclosure, when installed in an oven having an air frying mode, the amount of volatile organic compounds exhausted by the oven when cooking a predetermined food in the air fry mode under predetermined conditions are at least 95% lower than would be the amount of volatile organic compounds when cooking the predetermined food in the air fry mode under the predetermined conditions without the embodiments installed in the oven

Example embodiments include an oven comprising a cooking chamber including an air fry cook mode; a vent; a heated catalyst assembly located between the cooking chamber and the vent, the assembly including a housing having an inlet connected to the cooking chamber and an outlet connected to the vent; the housing containing a thermal radiation heat source located within the housing between the inlet and the outlet, the thermal radiation source including at least one looped element; a first catalyst located toward the inlet in proximity to one side of the thermal radiation source; and a second catalyst located in proximity to an opposite side of the thermal radiation heat source; the first and second catalysts arranged in planes parallel to that of the thermal radiation heat source. In embodiments, the first and second catalysts are selected from the group consisting of a screen catalyst, a wire mesh cloth, an expanded metal or metal foil, and a ceramic. A method for treating emissions of an oven when air frying include treating the air frying emissions within the heated catalyst assembly.

In other embodiments, a heated catalyst assembly is arranged for use with an oven having an air frying mode, the heated catalyst including a housing having an inlet connected to the cooking chamber and an outlet connected to the vent; the housing containing a thermal radiation heat source located within the housing between the inlet and the outlet, the thermal radiation source including at least one looped element, a first catalyst located toward the inlet in proximity to one side of the thermal radiation source, and a second catalyst located in proximity to an opposite side of the thermal radiation heat source; the first and second catalysts arranged in planes parallel to that of the thermal radiation heat source. The first and second catalysts are selected from the group consisting of a screen, a wire mesh cloth, an expanded metal or metal foil, and a ceramic. A method for treating emissions of an oven when air frying includes treating the air frying emissions within the heated catalyst assembly.

In yet other embodiments, no self-contained heated catalyst assembly is used. Rather, the embodiment may be in a form of a conversion kit for use in an oven including an air frying mode and a cooking chamber containing a circulation fan on a wall of the cooking chamber. The conversion kit includes a screen including a corrugated pattern and coated with a catalyst on at least half of the screen, the catalyst including a precious metal having a mass loading in a range of 20 g to 50 g per cubic foot of catalyst volume, the screen sized for installation on the inlet or suction side of the circulation fan and including means for connection to the inlet or suction side of the circulation fan. In a method of use, air frying emissions are passed from the circulation fan through the screen.

In yet other embodiments, the conversion kit may include one to four metal foil catalysts. The oven includes a cooking chamber including an air fry cook mode; a fan located at the back of the oven; a plurality of heating elements adjacent to and surrounding the fan to form four corners located about the fan; and the one to four metal foil catalysts, each metal foil catalyst located between a corresponding one of the four corners and the fan; and a baffle cover plate covering the fan, the plurality of heating elements, and the one to four metal foil catalysts. In a method of use, the air frying emissions pass through the fan where the emissions are contacted by the metal foil catalysts. 

What is claimed:
 1. A catalyst for use in cooking chamber of an oven having an air frying mode and including a circulation fan and heating elements and a baffle cover plate in proximity to the circulation fan, the catalyst adapted for connection to at least one of a suction side and a discharge side of the circulation fan, the catalyst comprising: at least one precious metal selected from the group consisting of platinum, palladium, and a mixture of platinum group metals, a mass loading of the at least one precious metal is in a range of 10 g to 75 g per cubic foot of catalyst volume; wherein, without the catalyst installed the oven emits a first amount of volatile organic compounds when cooking a predetermined food in air fry mode under predetermined conditions; wherein, with the catalyst installed the oven emits a second amount of volatile organic compounds at least 95% lower than the first amount of volatile organic compounds when cooking the predetermined food in the air fry mode under the predetermined conditions.
 2. The catalyst of claim 1, further comprising a screen including a corrugated pattern and coated with the catalyst on at least half of the screen.
 3. The catalyst of claim 2, wherein 75% to 100% of the screen is coated.
 4. The catalyst of claim 2, further comprising a rim surrounding the screen, the rim including locations for attachment to the at least one of a suction side and a discharge side of the circulation fan.
 5. The catalyst of claim 2, wherein the screen is a 30-mesh woven wire cloth.
 6. The catalyst of claim 1, further comprising a foil bundle having a cell density in a range of 20 cells to 50 cells per square inch, the foil bundle located in a corner of the heating elements.
 7. The catalyst of claim 6, further comprising a cell pattern selected from the group consisting of skew and herringbone.
 8. The catalyst of claim 6, further comprising another foil bundle located in another corner of the heating elements.
 9. The catalyst of claim 1, wherein emissions containing the volatile organic compounds is recycled through the catalyst prior to being exhausted by the oven.
 10. A method for treating emissions of an oven when air frying, the oven including a circulation fan and heating elements and a baffle cover plate in proximity to the circulation fan, the method comprising: treating air frying emissions by passing the air frying emissions through a catalyst adapted for connection to at least one of a suction side and a discharge side of the circulation fan, the catalyst comprising: at least one precious metal selected from the group consisting of platinum, palladium, and a mixture of platinum group metals, a mass loading of the at least one precious metal is in a range of 10 g to 75 g per cubic foot of catalyst volume; wherein, without the catalyst installed the oven emits a first amount of volatile organic compounds when cooking a predetermined food in air fry mode under predetermined conditions; wherein, with the catalyst installed the oven emits a second amount of volatile organic compounds at least 95% lower than the first amount of volatile organic compounds when cooking the predetermined food in the air fry mode under the predetermined conditions.
 11. The method of claim 10, wherein the catalyst comprises a screen including a corrugated pattern and coated with the catalyst on at least half of the screen.
 12. The method of claim 11, wherein 75% to 100% of the screen is coated.
 13. The method of claim 11, wherein the catalyst includes a rim surrounding the screen, the rim including locations for attachment to the at least one of a suction side and a discharge side of the circulation fan.
 14. The method of claim 11, wherein the screen is a 30-mesh woven wire cloth.
 15. The method of claim 10, wherein the catalyst includes a foil bundle having a cell density in a range of 20 cells to 50 cells per square inch, the foil bundle is located in a corner of the heating elements.
 16. The method of claim 15, wherein the foil bundle includes a cell pattern selected from the group consisting of skew and herringbone.
 17. The method of claim 15, wherein another foil bundle is located in another corner of the heating elements.
 18. The method of claim 12, wherein emissions containing the volatile organic compounds is recycled through the catalyst prior to being exhausted by the oven.
 19. A conversion kit for an oven including an air fry mode and having a circulation fan and heating elements and a baffle cover plate in proximity to the circulation fan, the conversion kit comprising: a catalyst adapted for connection to at least one of a suction side and a discharge side of the circulation fan, the catalyst comprising: at least one precious metal selected from the group consisting of platinum, palladium, and a mixture of platinum group metals, a mass loading of the at least one precious metal is in a range of 10 g to 75 g per cubic foot of catalyst volume; the catalyst further including at least one of a screen and a foil bundle, the screen sized for connection to the circulation fan and including a corrugated pattern and coated with the catalyst on at least half of the screen, the foil bundle having a cell density in a range of 20 cells to 50 cells per square inch and sized for location in a corner of the heating elements, the foil bundle further including a cell pattern selected from the group consisting of a skew pattern and a herringbone pattern; and a set of instructions for installing the catalyst in the oven.
 20. The conversion kit of claim 19, wherein the mass loading is in a range of 20 g to 50 g per cubic foot of catalyst volume. 